Minimally invasive percutaneous medial plate rod osteosynthesis for treatment of bicondylar humeral fractures in dogs: Surgical technique and case report.

OBJECTIVE: To describe a minimally invasive surgical technique for the treatment of comminuted humeral bicondylar (also known as T-Y) fractures in dogs and report outcome in 3 cases. STUDY DESIGN: Surgical technique description and case report. ANIMALS: Three consecutive dogs with traumatic comminuted humeral T-Y fractures. METHODS: Dogs that presented with a traumatic humeral T-Y fracture were prospectively included. The condylar component of the fractures was reduced first by using a combination of percutaneous forceps and K-wires. A transcondylar screw was applied, and epicondylar pins were preplaced medially and laterally. The metaphyseal component of the fracture was then reduced and stabilized with the pins. Finally, a bone plate was applied percutaneously along the medial humeral surface. Intraoperative fluoroscopy was used throughout surgery in all cases. Postoperative alignment in the frontal and sagittal planes was compared to the contralateral limbs. Time to clinical union, clinical outcome, and complications were recorded. RESULTS: Three dogs were included. Body weight ranged from 5.9 to 40 kg. Incomplete ossification of the humeral condyle was identified as the primary pathology leading to the fracture in 2 cases. All cases experienced uncomplicated healing with good to excellent functional recovery. CONCLUSION: The reported technique was associated with good outcomes without complications in 3 cases. CLINICAL SIGNIFICANCE: This study provides evidence that minimally invasive plate osteosynthesis represents an alternative to open reduction and internal fixation in the treatment of comminuted humeral T-Y fractures.

Minimally invasive percutaneous medial plate-rod osteosynthesis for treatment of humeral shaft fractures in dog and cats: Surgical technique and prospective evaluation.

OBJECTIVE: To describe and prospectively report outcomes associated with a novel minimally invasive percutaneous osteosynthesis (MIPO) technique for the treatment of humeral fractures in dogs and cats. STUDY DESIGN: Prospective clinical case series. ANIMALS: Eleven dogs and 4 cats with traumatic nonarticular humeral fractures. METHODS: Dogs and cats that presented with traumatic humeral fractures were enrolled in the study. After closed reduction, the fracture was stabilized by using a plate-rod combination applied via remote medial incisions. Postoperative alignment in the frontal and sagittal planes was statistically compared with the contralateral limbs. Time to clinical union and complications were also recorded. RESULTS: Eleven dogs and 4 cats were included in this study. Body weight ranged from 4.5 to 33.6 kg in dogs and from 2.2 to 3.6 kg in cats. A veterinary cuttable plate (6/11 dogs and 3/4 cats) or locking compression plate was used in a plate-rod configuration (11/11 dogs and 2/4 cats) or alone (2/4 cats). Rod-to-medullary-cavity ratio was 30%. Plate-span ratio was 5.8 (range, 2-13.5). No significant differences were found in frontal or sagittal plane alignment. Healing time in cases that completed on-time follow-up (12/15) was 36 ± 14 days (range, 20-69). No major complications were recorded. CONCLUSION: The reported technique was associated with good outcomes in a large variety of fracture configurations and animal sizes, with no complications. CLINICAL SIGNIFICANCE: This report provides evidence that MIPO is a compelling alternative to open reduction and internal fixation in the treatment of various humeral fractures.

Minimally invasive lag screw fixation of sacroiliac luxation/fracture using a dedicated novel instrument system: Apparatus and technique description.

OBJECTIVE: To describe a novel Sacroiliac Luxation Instrument System (SILIS™) and its application in minimally invasive osteosynthesis (MIO) of sacroiliac luxations/fractures (SIL/F). The SILIS was designed to provide stable SIL/F reduction and accurate sacral screw placement while reducing personnel exposure to ionizing radiation during intraoperative fluoroscopy. STUDY DESIGN: Descriptive, proof of concept cadaveric study. METHODS: A right SIL and a left SIL/F were created on a Labrador Retriever that had died of natural causes. Bilateral sacroiliac lag screw fixation was performed under fluoroscopic guidance with the SILIS, which consists of dedicated reduction and fixation instruments rigidly linked to table-bound 6-axis arms. RESULTS: Throughout surgery, the SILIS facilitated and maintained stable reduction and allowed accurate placement of a custom designed drill guide over the sacral body without the surgeon's manual holding of any reduction or fixation instruments. The surgical team was therefore able to step away from the C-arm when acquiring fluoroscopic images, thus reducing exposure to radiation. Dorsoventral and craniocaudal screw deviation from an ideal trajectory ranged from 0.9° to 3.8°. Both screws were fully located within the sacral body. CONCLUSION: The SILIS addresses limitations associated with MIO of SIL/F, including maintenance of reduction throughout surgery along with reliable and accurate sacral screw placement. Distance from the X-ray source is the most effective protection against radiation. Use of the SILIS allows the surgical team to move away from the C-arm during fluoroscopy, thereby reducing personnel exposure to dangerous direct and back-scattered ionizing radiation.

Comparison of open reduction versus minimally invasive surgical approaches on screw position in canine sacroiliac lag-screw fixation.

OBJECTIVE: To compare accuracy and consistency of sacral screw placement in canine pelves treated for sacroiliac luxation with open reduction and internal fixation (ORIF) or minimally invasive osteosynthesis (MIO) techniques. METHODS: Unilateral sacroiliac luxations created experimentally in canine cadavers were stabilized with an iliosacral lag screw applied via ORIF or MIO techniques (n = 10/group). Dorsoventral and craniocaudal screw angles were measured using computed tomography multiplanar reconstructions in transverse and dorsal planes, respectively. Ratios between pilot hole length and sacral width (PL/SW-R) were obtained. Data between groups were compared statistically (p <0.05). RESULTS: Mean screw angles (±SD) were greater in ORIF specimens in both transverse (p <0.001) and dorsal planes (p <0.004). Mean PL/SW-R was smaller (p <0.001) in the ORIF group, yet was greater than 60%. While pilot holes exited the first sacral end-plate in three of 10 ORIF specimens, the spinal canal was not violated in either group. CONCLUSIONS: This study demonstrates that MIO fixation of canine sacroiliac luxations provides more accurate and consistent sacral screw placement than ORIF. With proper techniques, iatrogenic neurological damage can be avoided with both techniques. The PL /SW-R, which relates to safe screw fixation, also demonstrates that screw penetration of at least 60% of the sacral width is achievable regardless of surgical approach. These findings, along with the limited dissection needed for accurate sacral screw placement, suggest that MIO of sacroiliac luxations is a valid alternative to ORIF.

In vivo biomechanical evaluation of a novel angle-stable interlocking nail design in a canine tibial fracture model.

OBJECTIVE: To compare clinical outcome and callus biomechanical properties of a novel angle stable interlocking nail (AS-ILN) and a 6 mm bolted standard ILN (ILN6b) in a canine tibial fracture model. STUDY DESIGN: Experimental in vivo study. ANIMALS: Purpose-bred hounds (n = 11). METHODS: A 5 mm mid-diaphyseal tibial ostectomy was stabilized with an AS-ILN (n = 6) or an ILN6b (n = 5). Orthopedic examinations and radiographs were performed every other week until clinical union (18 weeks). Paired tibiae were tested in torsion until failure. Callus torsional strength and toughness were statistically compared and failure mode described. Total and cortical callus volumes were computed and statistically compared from CT slices of the original ostectomy gap. Statistical significance was set at P < .05 RESULTS: From 4 to 8 weeks, lameness was less pronounced in AS-ILN than ILN6b dogs (P < .05). Clinical union was reached in all AS-ILN dogs by 10 weeks and in 3/5 ILN6b dogs at 18 weeks. Callus mechanical properties were significantly greater in AS-ILN than ILN6b specimens by 77% (failure torque) and 166% (toughness). Failure occurred by acute spiral (control and AS-ILN) or progressive transverse fractures (ILN6b). Cortical callus volume was 111% greater in AS-ILN than ILN6b specimens (P < .05). CONCLUSIONS: Earlier functional recovery, callus strength and remodeling suggest that the AS-ILN provides a postoperative biomechanical environment more conducive to bone healing than a comparable standard ILN.

Effect of screw insertion torque on mechanical properties of four locking systems.

OBJECTIVE: To evaluate the effect of screw insertion torque on the mechanical properties of four 3.5 mm locking systems: New Generation Devices (NGD), Securos (PAX), Synthes (SYN), and Veterinary Orthopedic Implants (VOI). STUDY DESIGN: In vitro mechanical study. METHODS: Screws were inserted at 1.5 Nm, 2.5 Nm, and 3.5 Nm torques, using dedicated drill guides and a calibrated torque screwdriver. Locking mechanisms were tested under shear loading conditions using a custom-design probe. Tests were conducted under displacement control until failure. Load to failure and interface stiffness were compared between and within groups using a two-factor ANOVA (P < .05). Failure modes were described. RESULTS: The SYN group had significantly greater mechanical properties compared to all other groups at any given insertion torque. Insertion torque had a significant effect on the PAX group, increasing the load to failure by 126% when increasing the insertion torque from 1.5 Nm to 3.5 Nm. Insertion torque had no significant effect on the mechanical properties of the VOI group and limited effect on the NGD and SYN groups. Single failure mode, by screw head decoupling or screw shaft fracture, occurred in the SYN and VOI groups, respectively. In contrast, NGD and PAX systems failed through a combination of screw decoupling and/or bending. CONCLUSIONS: Regardless of insertion torque, the SYN locking mechanism showed the highest failure loads, interfacial stiffness as well as consistent failure mode. These findings highlight the dependability of this system. When using the PAX system an insertion torque of at least 2.5 Nm should be recommended.

In vitro evaluation of the effect of fracture configuration on the mechanical properties of standard and novel interlocking nail systems in bending.

OBJECTIVE: To investigate the effect of fracture configuration on the mechanical properties of standard interlocking nails (ILNs) and a novel angle-stable ILN (ILNn) in bending. STUDY DESIGN: In vitro experimental study. SAMPLE POPULATION: Synthetic tibial gap fracture bone models. METHODS: Bone models, featuring a 5 or 120 mm central defect, respectively, mimicking a simple diaphyseal and a comminuted fracture involving both metaphyses, were implanted with 6 or 8 mm screwed or bolted standard ILNs (ILN6s, ILN6b, ILN8s, ILN8b, respectively) or an ILNn. Specimens were tested in 4-point bending. Construct angular deformation (AD) and slack were statistically compared (P<.05). RESULTS: With increasing gap size, standard ILN construct AD increased significantly by approximately 27% in ILN8b and by up to 105% in ILN6s. Similarly, standard ILN construct slack significantly increased by approximately 33% in ILN8b (from approximately 4.2 degrees to approximately 5.6 degrees) and by up to approximately 130% in ILN6s (from approximately 7 degrees to approximately 16 degrees). Conversely, there was no difference in the ILNn construct AD (approximately 4 degrees) regardless of gap size. ILNn AD was the lowest of all groups and occurred without slack. CONCLUSIONS: This study demonstrated that the angle-stable ILNn provided construct stability regardless of fracture configuration, whereas the intrinsic slack of standard ILNs could jeopardize construct stability in a fracture configuration involving the metaphyses. CLINICAL RELEVANCE: Use of standard ILNs may be optimal in diaphyseal fractures where circumferential nail/cortical contact could augment repair stability. Conversely, the angle-stable ILNn may represent a reliable fracture stabilization method for diaphyseal fractures as well as fractures involving the metaphyseal regions.

In vitro mechanical evaluation of medial plating for pantarsal arthrodesis in dogs.

OBJECTIVE: To compare the bending properties of pantarsal arthrodesis constructs involving either a commercially available medial arthrodesis plate (MAP1) or a specially designed second-generation plate (MAP2) implanted in cadaveric canine limbs and evaluate the effect of calcaneotibial screw (CTS) augmentation on the structural properties of both constructs. SAMPLE POPULATION: 5 pairs of canine hind limbs. PROCEDURES: Within pairs, specimens were stabilized with an MAP1 or MAP2 and loaded to 80% of body weight, with and without CTS augmentation. Compliance, angular deformation (AD), and plate strains were compared. RESULTS: Construct compliance and AD did not differ between plates. Maximum plate strain was lower in the MAP2 than in the MAP1 (difference of approx 30%). Augmentation with a CTS reduced compliance, AD, and strains in MAP1 constructs but had no effect on those variables in MAP2 constructs. CONCLUSIONS AND CLINICAL RELEVANCE: Because of lower peak strains, the MAP2 may be less susceptible to failure than the MAP1. Furthermore, CTS augmentation was unnecessary with MAP2s, which could minimize intra- and postoperative morbidity. Compared with what is known for dorsal plates, MAP2 constructs were associated with approximately 35% less AD. As a result of improved local stability, one might anticipate earlier fusion of the talocrural joint with an MAP2. In addition, plate peak strain was approximately 3.5 times lower in MAP2s than in dorsal plate constructs, which should result in greater fatigue resistance. The use of MAP2s may be a better alternative to both MAP1s and dorsal plates and could contribute to lower patient morbidity.